Developed by Handmark, TweetCaster offers a free ad-supported version and a non-ad $4.99 professional version. Designed for iPhone, iPad, and iPod Touch users, the app made its debut in the App Store this week following its one-year anniversary in the Android Market.

Opening the app initially displays a screen where you can see the top tweets of the day and categories of suggested Tweeters that you may want to follow. From there, logging into your own account brings up the familiar Twitter timeline.

The interface is nicely designed. It's colorful but clean, with none of the frills or clumsy dialogue balloons found in other Twitter apps.

Tapping the home button on the bottom menu bar displays a timeline of the tweets you follow. Your own tweets are highlighted by a yellowish tint, so you can easily identify them. The menu bar also offers icons to view tweets in which you're mentioned, direct messages, and favorite tweets.

Viewing tweets from your timeline works well. Clicking on a URL within a tweet opens up a browser-type window to let you view the content. You can easily respond to, retweet, or e-mail an existing tweet. There's even an option to "zip" or temporarily mute tweets based on a specific person, trend, or keyword, a handy option if you're getting tired of all those tweets about Charlie Sheen. The one limitation I found here is that the app only works in portrait mode, so there's no way to view tweets or their linked content in landscape.

Posting a new tweet also works cleanly. I liked the way the app gives you access to your followers and followees to let you send direct messages. You can easily attach a photo, either by snapping a new one or grabbing one from your library. You can also attach a link to any piece of music stored on your device. That link then points to that particular music in iTunes in case your followers want to purchase it. This feature only seems to work for music, because when I tried to link to podcasts, it failed to open the right content in iTunes.

TweetCaster can lead you to a variety of useful Twitter features, all from a single window launched from the menu bar. You can view all the tweets that you've retweeted as well as those that your followees have retweeted. You can see all of the Twitter lists that you follow or that follow you. And you can view the latest trending topics.

The app also provides quick access to your followers and followees where you can drill down to see the details and photos for each specific account. And thankfully, TweetCaster provides an accurate number of your tweets and Twitter followers, which some Twitter apps fail to do. You can manage multiple Twitter accounts, always a nice option for these kinds of apps. Ever further, you can tap into your Facebook account to send a Tweet to your Facebook status line.

TweetCaster provides an option to add icons for different features to the menu bar by dragging and dropping them. In my initial testing, this didn't seem to work. But then I discovered that you have to hold your finger on one of the icons for a second in order to activate the feature. You can then move any of your favorite icons directly to the menu bar.

My only real complaint is that the app was slow at times. Scrolling through tweets and lists, loading older tweets, and jumping from one section to another wasn't as quick as I've found in other Twitter apps.

Though I didn't test the free ad-supported version, a Handmark rep told me that it works the same as the paid version except for its display of banner ads. Users can upgrade to the pro version from within the free version through an in-app purchase.

Update, 11:15 p.m. PST: The story now reflects further testing done on adding icons for different features to the menu bar by dragging and dropping them.